That sounds an awful lot like browser JS/HTML/CSS standards. Or perhaps the OpenGL standard. Doubtless you'd have a long incubation period of inconsistent cross-application behavior, and a proliferation of vendor-specific extensions.
Microsoft would have to be involved in any such effort for it to amount to anything, and I'm not sure they really have much incentive to do so - unless it is along the lines of, "here, LibreOffice, this is our document API, go implement it, and, by the way, make it compatible with all these legacy VBA scripts out in the wild".
I agree to a point, but actually Microsoft wouldn't have to be heavily involved really. With ODF, that push didn't come from Microsoft and eventually landed with standards bodies. Microsoft fought it all the way, and even though they muddied the water with OOXML, they had to stop implementing binary, opaque and hard to manipulate file formats.
They were then forced (by market demand) to implement ODF. I can see something similar happening in terms of document automation: only maybe this time it might be quicker given there is experience around the DOM in web browsers already, so a model is already usable.
Microsoft would have to be involved in any such effort for it to amount to anything, and I'm not sure they really have much incentive to do so - unless it is along the lines of, "here, LibreOffice, this is our document API, go implement it, and, by the way, make it compatible with all these legacy VBA scripts out in the wild".